Saturday, February 8, 2014

A journaling file system is more reliable when it comes to data storage.
Journaling file systems do not necessarily prevent corruption, but they
do prevent inconsistency and are much faster at file system checks than
non-journaled file systems. If a power failure happens while you are
saving a file, the save will not complete and you end up with corrupted
data and an inconsistent file system. Instead of actually writing
directly to the part of the disk where the file is stored, it first
writes it to another part of the hard drive and notes the necessary
changes to a log, then in the background it goes through each entry to
the journal and begins to complete the task, and when the task is
complete, it checks it off on the list. Thus the file system is always
in a consistent state (the file got saved, the journal reports it as not
completely saved, or the journal is inconsistent (but can be rebuilt
from the file system)). Some journaling file systems can prevent
corruption as well by writing data twice.

The
most commonly used journaling file system, ext3fs (or third extended file
system) is an extension of ext2 with journaling capabilities. The ext3fs has
been supported in Linux since 2001. Finally, the ReiserFS journaling file system
blazed many new trails when it was introduced and found wide adoption. Its
evolution is now diminished because of the legal issues of its original author.

Journaling file systems
today

File System

Max File Size

Max Partition Size

Journaling

Notes

Fat16

2 GB

2 GB

No

Legacy

Fat32

4 GB

8 TB

No

Legacy

NTFS

2 TB

256 TB

Yes

(For Windows Compatibility) NTFS-3g is installed by default in Ubuntu, allowing Read/Write support

ext2

2 TB

32 TB

No

Legacy

ext3

2 TB

32 TB

Yes

Standard linux filesystem for many years. Best choice for super-standard installation.

ext4

16 TB

1 EiB

Yes

Modern iteration of ext3. Best choice for new installations where super-standard isn't necessary.

reiserFS

8 TB

16 TB

Yes

No longer well-maintained.

JFS

4PB

32PB

Yes (metadata)

Created by IBM - Not well maintained.

XFS

8 EB

8 EB

Yes (metadata)

Created by SGI. Best choice for a mix of stability and advanced journaling.